1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus which performs three-dimensional scanning.
2. Description of the Related Art
There is available an ultrasonic diagnostic apparatus which performs electronic scanning while mechanically moving a probe (mechanical scanning) for three-dimensional scanning (see Jpn. Pat. Appln. KOKAI Publication No. 10-179576). Performing electronic scanning while mechanically scanning a probe will be referred to as electronic/mechanical combination scanning. A probe for electronic/mechanical combination scanning has a transducer unit comprising a plurality of transducers arrayed in a line. A transmission unit controls the delay times of driving pulses to the transducer unit so as to sequentially switch ultrasonic scan lines. A delay-and-sum circuit delays and adds a plurality of echo signals received by the transducer unit to convert the signals into actual measurement scan line signals. The ultrasonic diagnostic apparatus generates a plurality of actual measurement scan line signals by mechanically scanning the probe in a direction in which the transducer unit crosses an electronic scan plane (in a direction generally perpendicular to the electronic scan plane) at the time of electronic scanning. Multislice tomograms are generated on the basis of a plurality of actual measurement scan line signals. A pseudo-three-dimensional image is generated by performing rendering processing of a set of generated multislice tomograms.
As an electronic/mechanical combination scanning method, a method of repeating electronic scanning while mechanically and continuously moving a transducer unit is available. In this method, however, an electronic scan plane tilts with respect to the direction of movement. In this case, actual measurement multislice tomograms tilting with respect to the direction of movement are generated on the basis of a plurality of actual measurement scan line signals constituting the electronic scan plane tiling with respect to the direction of movement. A pseudo-three-dimensional image is generated by performing rendering processing of a set of generated actual measurement multislice tomograms. However, this method requires complicated rendering processing, and hence is not practical. In addition, since electronic scan planes in forward and backward paths in mechanical scanning differ from each other, this method requires complicated rendering processing in consideration of the difference.
As shown in FIG. 13, there is available a method of intermittently moving the transducer unit such as moving→stopping→electronic scanning→moving→stopping→electronic scanning in order to make the electronic scan plane perpendicular to the direction of movement. This method, however, requires complicated control of a moving mechanism and of electronic scanning. Furthermore, the method is unsuitable for high-speed 3D scanning because the ultrasonic transducer unit is mechanically stopped.